Method of sublimation



July 6, 192e..I

C. A. LYFORD METHOD OF SUBLIMATION Filed April,2, 1920 j Patented vJuly. 6, 19216.

l. UNITED sTATss PATENT OFFICE#` CHAUNCEY A. LYFOBD, F EAST AURORA, NEW..YORK, ASSIGNOB TO NATIONAL IANI- l LINn a CHEMICAL! co., INC., or NEW YORK, N. Y., .A CORPORATION OF NEW YORK.

Marston or sUizLmArIoN.

Application tiled April 2,

method oflimation, and more particularly to the purilication of crude benzanthrone for the pur-l pose of separating it from the non-sub1imable impurities produced simultaneously therewith in the production of benzanthrone from anthraquinone or anthranol.

l In the production of benzanthrone, by the condensation of anthraquinone or anthranol with glycerine, there are simultaneously produced varying amounts of impurities from which it is necessary to separate the benzan partial] purified state. The impure crude benzantlirone, admixed with the impurities, is, after drying, a material of a brittle character'which is easil reduced to a fine powder when subjectedy to agitation. Because of its character, this material is not Well adapted forltreatment by sublimation in apparatus in which the material is agitated Vduring the sublimation, since the'fine dust of the material produced by the` agitation is carried over to a greater or less extent with the sublimate so that the sublimate is .contaminated by impurities.

In the ordinary forms of sublimers deficulty is also encountered because of local overheating of the material where `it comes in .contact with the Walls of the container, if .the container Walls are heated to a suffi# ciently high temperature to bring about the sublimation.A Such overheating may result in charring or gumming of the material near the heated walls, and uneven' heating of the charge as a-vvhole The provision of agitators reduces this difficulty of overheating or uneven heating, although this dliiicultyv may nevertheless be encountered to a greater or ess extent even when an agitator .1s prohowever, has the disadvantage above referred to that it pulverizes the material so that the fine dust of the crude material is carried lover as an impurity with. th'e s ublimate.

The present invention is based upon the discovery that crude benzanthrone can be purified from itsnon-sublmable impurities in -a simple and advantageous manner, and without the ditiicultiesarising fromV local overheating or frommec'hamcal agitation throne in order to obtain it inapuried or signed for work at highl temperatures dif-V through -the .charge 1920. semi no. s'm,ao1.

of the mass undergoin "sublimation, by placing the crude benzanirone in a suitable container or recegtacle upon -a perforated bottom and intro ueing superheated steam vor other heated gas or vapor beneath the perforated bottom so that it is caused to pass up therethrough and throu h the material supported thereon. .The-'su limed benzanthrone and sublimable' impurities, together with the transporting medium,`are conveyed from the ,sublimation receptacle to a sultable condenser Where the sublimate is separated in a solid state.

In carrying out the sublimation process of the present invention, the crude benzanV the throne will be progressively heated bg' and superheated steam passing therethroug will be gradually brought to the temperatureof sublimation. The crude material will Iirst be heated to a temperature Vof about 100o C. and may remain at this tem erature forv some time, even with the use o highly superheated steam, until any moisture con.

tained in the material has-been removed and i until such other reactions,` such as decomposition of sulfonated compounds and evolution of sulfur dioxide, this temperature,vhave taken place. Sublimation commences as soon as the material is superheated above 100 and proceeds with increasing speed as the temperature increases until the optimum temperature is reached.. When the optimum temperature has beenv attained, this temperature is continued until the sublimation is substantially completed, althou this temperature can with advantage' be somewhat increased at thejend of the operation to complete the sublimation. At any given temperature' at which the sublimation takes place, and With-V in certain limits of speed with which the superheated steam is admitted, the sublimaproaches the desired mg or decreasing the steam suppl or by varying the steam temperature. e rate at `which theA superheated steam isf passed and through `the sib:Y

whichv takes place at Ition goes on faster with the use of a greater It-will Hot-generally be the temperature higher .higher temperature. As the temperature ap# y temperature ofY oper-- ation, it maybe controlled either by increas-l 5 10 of removing the exhausted material at they limer should be sufficient to ermit but little cooling in the upper part o the apparatus, which should be well insulated.

The invention will be further described in connection with the accompanying drawings illustrating apparatus adapted for the practice of the invention. This apparatus is not claimed herein but forms the subject-matterv of a separate application, Serial No. 37 0,802, filed April 2, 1920.

ln the accompanying drawings:

Fig. l shows one form of sublimation apparatus in elevation and with parts in section; and

Fig. 2 1s a vertical'sectional View of a modiied form of apparatus.

In the apparatus of Fig. l the receptacle or container 1 is provided with a Suitable cover 2 having a charging manhole 3 therein and having an outlet conduit 4 for the sublimate, this conduit leading to the condenser 14. Thereceptacle or container l has a perforated bottom spaced away from the bot-- tom of the container itself and suitably suported (by means not shown). This perorated bottom is made up. of a perforated sheet metal plate 6 having a screen 7 supported thereby and upon which the charge of crude benzanthrone to be sublimed is supported. The screen 7 prevents smaller particles from falling through into the chamber 9 and insures a more uniform distribution of the heating and transporting medium passing upwardly therethrough. lThe perforated or false bottom divides the vessel or receptacle 1 into a larger upper chamber 8 and a smaller lower chamber 9. The chamber 8 has a side opening 10 for the purpose end of the operation.

The container l is surrounded by a heat- `ing jacket 11 intended for oil or other suitable medium. The oil jacket is heated and maintained at the desired temperature in any suitable manner, as by direct firing in the furnace .13. Thermometer wells 5 and 12 are suitably arranged in the chamber 8 and in the oil jacket. It will be evident that the oil used in the heating jacket should have a high flash point. The temperature of the oil or other heating medium in the jacket should be maintained only at about that point which y'will compensate for the possible heat losses of the superheated steam or other transporting medium passing through the apparatus. All the exposed metal parts of the apparatusl should be covered with magnesia packing or other insulating covering (not shown) to prevent condensation of the sublimate.

Where superheated steam is supplied las j the transporting medium it is 'superheated to the proper temperature in the superheater 23 which may be of any suitable constructioii, and which is shown as an oil-tired superheater having oil and. air supply pipes 24 and 25. The superheated steam, superheated to the proper temperature, is conveyed from the superheater through the pipe 26 and discharges at 27 into the lower chamber 9 below the false bottom. From this chamber it passes up through the perforated bottom in a uniform manner and then passes up through the charge of crude benzanthrone, serving to heat the material in a uniform manner and to the proper temperature. The sublimed benzanthrone is carried over with the superheated steam, through the pipe 4, to the condenser. The pipe 29 from the superheater to the top of the chamber 8 permits an excess of superhcated steam to be introduced to assist in sweeping the vapors from the chamber to the condenser.

The condenser illustrated is provided with a. water jacket 15 and with scrapers 16 for keeping the inside cooling surfaces free from any benzanthrone that condenses thereon, thereby promoting the cooling elfect of the water jacket. The condenser is also provided with spray nozzles 18 and 19, one for spraying water downwardly at the top and the other for spraying water upwardly from the bottom. TWater is supplied through the pipe 17. The benzanthrone and the water condensed in the condenser are passed to a filter for the separation of the benzanthrone from the water. As illustrated, this filter is in the form of a perforated plate 20 having a canvas layer 2l thereon. The benzanthrone is collected on the ilter while the wateris drawn olf through the pipe 22 to a suction pump (not shown).

In the operation of the apparatus, the 'charge of crude benzanthronc, for example, the dry crude benzanthrone press-cake in lumps about the size of English walnuts, is charged into the compartment 8 through the manhole 3, the manhole cover is secured in place, the oil jacket is heated, for example, to a temperature of about 285 C., and the superheated steam is introduced through the pipe 27 into the lower chamber 9 from which it passes upwardly through the false bottom and through the charge supported thereby. In starting the operation, the oil burners under the oil jacket and the superheater, can be simultaneously started and the temperature of the oil jacket and of the steam gradually increased to the desired temperature, as indicated by thermometers placed in the thermometer wells 5 and 12.

The temperature of the steam is quickly raised by the superheater to a suitable temperature, -for example` of about 325 where it can be maintained throughout the l operation. to atemperature of C., at which steam is no longer condensed within the apparatus, the bleeder or draw-ofi' pipe 28 is kept open so that water may drain off. When Until the whole apparatus comes 1 no longer condenses this opening The supply of steam passin apparatus is in part determine pacity of the condensing apparatus the steam is closed. through the by theca and is adJusted to that capacity. In the or- 10. it reaches the perature of about 225 dinary operation ofthe apparatus, a considerable time may be required to bring the charge to 100 or thereabove, after which the temperature mounts more rapidly until temperature at which the main sublimation fis to take place. With th gradual heating of the apparatus, a period of a-'few hours may be required for attaining this-temperature, for example, a tem- C., or a maximum temperature o f about 250 C. When the sublimation is completed, as indicated by the fact that no more collects in the condenser and receiver, the heating of the oil jacket and of the steam is discontinued, and

a smallsupply of ordinary steam, not superheated, is kept going through the apparatus for the urpose of keeping air awayfrom the unsu limed residue until the temperature l has 'fallen to about v125 C. This maintenance of the steam supply prevents inow Y of air tothe apparatus andA setting lire to the residue.

The crude benzanthrone charged into the SOapparatus is advantageously the dried pres- '35 a non-porous mass.

cake in the .form of lumps of a suitable size, inasmuch as the dried material gives a porous mass Well adaptedfor the sublimation, while the undried press-cake tends to give The current of. superheated steam is not allowed to rush through the apparatus but/is regulated so that an L even, gentle flow is obtained -which prevents mechanical Vlosses by the carrying over of crude material with the subli'mate. The residue remaining in the apparatus at the i end of the sublimation 1s made up of the unsublimable impurities of the crude benzanthrone. This residue @is relatively bulky, and varies'in amount, depending upon the particular methodby'which the crude ben zanthrone was produced. This residue is l' withdrawn from the apparatus through the opening 10. L j i The sublimate, made up mainly of the/sublimed benzanthrone, together with any sublimable im urities that accompanywit, and together with the superheated steam, pass through the pipe 4 to the condenser wherel condensation 1s eiectedgmd where the sublimate is collected on the ilter 21. The condensation can be effected either by means of the Water iacket introduced through the spray nozzles 18 andl l0 19, or by. the combined use of the water jacket and the s ra The .method o eecting the condensation f the -sublimate determines its physical state. If the sublimed benzanthronefis coni5 densed upon the cold surface' of the water fment in the purity v d `where it still contains a 15 or by means of the spray' jacket, it is in a harder, calzy condition requlring subsequent grinding.. It is more advantageous tobring about the condensation, y .by means of the water spray, masmuch as the benzanthrone can thus be obtained in a line, soft condition. `The warmer the condensing chamber, the softer and the more desirable for certain purposes is the physical condition of the material. y The production of a productof this character is effected by slow condensation in a warm chamber condensed with the waterv spray, vand the product is sepa-rated by suction filtration,

`such soluble product or products as may be admixed withit are to a greater or less extent washed away. with resultingimproveof the sublimed product; while the product condensed v by cooling` without the 'Water spray, and dried without washing, has a more variable melting point.

When the .sublimatc' It 1s accordingly, of advantage to bringabout the condensation With the Water spray so vthat the steam and benzanthrone are condensed and admixed with-the added water and the benza-n'throne obtained in a finely divided state and washed with the `water before it is finally separated.

While other suitable ases or vapors than superheated steam can e used for carrying out the sublimation when heated tothe requisit'e temperature, and provided proper precautions are taken, nevertheless the use of superheated steam is particularly advantageous in the carrying out of the process as well as in the condensation of the sublimate,

inasmuch as the condensation of the admlXed steam and benzanthrone vapors givesv land uil'y and more dense noA los

unlessprecaution uct may be Iobtained containlng varying4 amounts of the anthroquinone admixed with the benzanthrone.` The benzan'throne produced according to the resent invention, mixed sublimable impurities, .suchasanthraquinone, may be subjected to further purification to free it from such impurities. The sublimed 'beuzanthrone can, however, be used directly withoutv puriicationfwhere the impurities are 'present in unobjectionableamount/ or where they do not interfere with the treat-v ment to which the benzan'throneis to be subse uentlysubjected, or the use to which it is to e put. 1

Instead of purifying crude benzanthrone and separating the benzanthrone from the non-volatile matrix of impurities with which it is admixed, the process of the present invention is also applicable to the treat-- ment of a purified benzanthrone for the purpose of changing its physical condition.

In the apparatus of Fig. 2 the corresponding parts are indicated by the same reference numerals with the suiiix a appended thereto. In the construction illusi trated in' this ligure, however, the oil jacket 'is omitted and a steam jacket is provided adapted to be 'heated by the same steam which is used in carrying out the sublimation operation. The apparatus comprises the receptacle 1 having a perforated bottom for containinfJr the charge ofv material to be sublimed, and.) this receptacle is surrounded by an outer receptacle. 11 which provides an annular steam jacket and a bottom com tion of supplying the heat for the heating jacket and the steam for the sublimation, so that the receptacle 1 is surrounded by steam at substantially the same temperature as that which is passing through it or effecting the sublimation. Proper regulation of the steam temperature thus enables the en ltire sublimation operation to be properly regulated-in temperature.

From the above description it will be seen that the sublimation of the benzanthrone is effected without local overheatin or uneven heating of the charge and wit out mechanical agitation thereof. As a result the production of fine dust is avoided and .the carrying over of fine dust Vwith the steam and sublimate is likewise avoided. The only agitation to which the charge is sub.-

jected 1s that incident to the passage of the steam upwardly therethrough, but this will ordinarily be so slight that it will be entirely nnobjectionable vand may even be desirable in promoting the uniformity of distribution of the steam through thematerial.

Avention is especially adapted The improved method of the present infor treating such materials as benzanthrone, etc., because the materlal is sublimed without agitation,

ythe'container or receptacle, namely,

. mation by passing the heating agent.

so that dusting is'eliminated, as well as v local overheating. The material is supported out of contact with the hottest portion of the bottom, and inl such position that the heating and transporting agent may have access to every part thereof.- That is, such agent must pass through the material, and the material vis so supported that it is permeable thereto. v J

I claim:

1. The method of effecting the .sublima-` tion of benzanthrone, which comprises heating the bcnzanthrone to the point of sublimation by passing through thermateria'l a suitable gaseous heating and Atransporting agent, heated to a temperature -higher than that at which the benzanthronesublimes, and j carrying away the sublimate by such heating and transportin al ent. Y

2. The method o tion of benzanthrone, which comprises heating the benzanthrone to the point'of sublithrough thematerial a suitable gaseous heating and transporting agent, heated to a tempera ure igherthan that at which the benzan hrone sublimes, andcarrying awayl heating and transporting agent, and supporting the benzanthrone in such manner. that it will be permeable throughout its mass to the agen-t.

r3. The method of effecting the Sublimation of benzanthronel, which comprises heating sublimation by passing through the material a suitable gaseous heating and transporting `a ent, heated to atempera'ture higher than t at at which the benzanthrone sublimes, and carryin away the sublimate by such heating an transporting agent, supporting the benzanthrone '1n such manner that it will be permeable throughout its mass to the agent, and condensing together the sublimate and 4. The method of effecting the sublimation of benzanthrone, which comprises heating the benzanthrone to the point of sublimation by passing through the material a suitable gaseous eating and transporting agent, heated to a temperature higher than that at vwhich the benzanthrone sublimes, carrying away the sublimate by such heating and transporting agent, su porting the benzanthrone in such manner meable throughout its mass to the agent, 'and condensing to ether the sublimate andthe heating agent y means of a spray of cooling liquid, whereby a finely divided product is obtained.

5. The method of effecting the sublimation of benzanthrone, which comprises passingupwardly through the mass of benzanthrone a current of superheatedsteam at a temperature of 225 to 250'.G., and aftere ecting the sublimathe sublimate by such the benzanthrone to the point ofi at it will be per-V wards condensing the steam and the volatilized benzanhrone.

6. The method of effecting the sublimation of benzanthrone, which comprises subj ecting the same to the action of superheated steam heated to atemperature of about 225 to 250 C. passed through the benzanthrone in xvtimate contact with every part thereof.

7. The method of eiectin the sublimation ci' crude benzanthrone, w ich comprises charging a body of the dry crude benzenthrone, largely in the form of small lumps` l in `such manner that a gaseous heating agent may pass upwardly through the benzanthrone, introducing superheated steam up- 15 wardly through the charge of material at a temperature appropriate to the sublimation and condensing the admixed sublimate and steam to give the benzanthrone in a nely divided state. 2

In testimonywhereof I afiix Am signature.

i CHAUNCEY A. L'FORD. 

